The invention relates generally to storage management for computer systems. More particularly the invention relates to tracking the extent to which data sets are enlarged and/or reduced in size over their lifetime and using this information to assist in making decisions when allocating the same data set in a subsequent instantiation. As will be recognized by those of ordinary skill in the art, data sets are the means by which an operating system manages storage. By way of example, in the z/OS operating system the term data set refers to a file that contains one or more records so that a data set may be thought of as any named group of records. Accordingly, as used herein the term “data set” refers to any aggregate collection of storage allocated and/or managed by an operating system.
One of the greatest abusers of direct access storage device (DASD) space is the data set that is consistently over allocated, where space may or may not be released at data set close. With products such as MAINVIEW® Storage Resource Manager StopX37/II by BMC Software, the assumption is generally made that most data sets are under-allocated and storage is added as needed. (MAINVIEW is a registered trademark of BMC Software, Inc.) While this may be correct in theory, it is often not the case in practice. If a user is testing a new application, they will often use Job Control Language (JCL) that is intended for production work. Since tests generally use a smaller subset of data than does the production application, the allocations from the production JCL will often be too large. Thus, the data sets allocated may be substantially larger than they need to be. The excess storage wastes space on DASD.
Thus, it would be beneficial to provide a means to track the amount of storage used by a data set during the course of its life-time and, during a subsequent instantiation, allocate its storage based on this prior observed behavior.